One of the most challenging problems in the field of artificial hip joints is the wear debris caused by articulation between the surfaces of the polyethylene acetabular cup and the metal or ceramic hip joint head. Even at a low wear rate such as 0.1 mm per year, the debris resulting from this wear is considered to be significant because it enters the vascular system of the human body and may cause osteolysis.
Some investigators have proposed reducing the wear problem by a variety of different methods. For example, U.S. Pat. No. 5,378,228 ("Schmalzried") suggests surrounding the prosthetic device with a series of funnels and reservoirs. U.S. Pat. No. 5,514,184 ("Doi") suggests providing a protector along the outer edge of the cup to catch debris. U.S. Pat. No. 4,822,368 ("Collier"), EPO Published Application No. 0 346 294 ("Impallomeni"), and U.S. Pat. No. 5,514,182 ("Shea") each suggest surrounding at least one of the articulation surfaces with a semi-permeable membrane which permits fluid circulation but traps debris. However, each of these systems adds greatly to the complexity of the prosthesis.
Therefore, there is a need for a simple bioprosthetic system which reduces the danger caused by articulation-induced wear.